Bandwidth adaptation for dynamic adaptive transferring of multimedia

ABSTRACT

Bandwidth adaptation is achieved with selection of quality levels of media content to be transferred based on network conditions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit as a Continuation of U.S. patentapplication Ser. No. 14/359,859, filed May 21, 2014, now U.S. Pat. No.10,397,294, issued on Aug. 27, 2019, which claims benefit as a NationalStage Entry (371) of International Application No. PCT/US2012/068990,filed Dec. 11, 2012, which claims the benefit, under 35 U.S.C. 119(e),of prior provisional application 61/576,334, filed on Dec. 15, 2011. Theabove-mentioned patent applications are assigned to the assignee of thepresent application and are hereby incorporated by reference as if fullyset forth herein. The applicant(s) hereby rescind any disclaimer ofclaim scope in the parent application(s) or the prosecution historythereof and advise the USPTO that the claims in this application may bebroader than any claim in the parent application(s).

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

TECHNICAL FIELD

The present disclosure relates to delivering media content over theInternet. More particularly, an embodiment of the present inventionrelates to bandwidth adaptation for dynamic adaptive transferring ofmultimedia.

BACKGROUND

With the modern internet, hypertext transfer protocol (HTTP) based mediatransferring is practically ubiquitous. Content providers typicallydeploy their media delivery service on top of the internetinfrastructure. For example, content providers like Netflix do notdeploy their own streaming architecture and can use the internetinfrastructure as is. With the internees infrastructure of caches,content distribution networks (CDN) and proxies, HTTP was designed forbest effort file delivery, rather than real time media delivery.Conventional streaming protocols such as real time transport protocol(RTP) do not typically exploit this infrastructure, which, unlike HTTP,may also be constrained by Network Address Translation (NAT)complexities and firewall traversal requirements.

Being stateful (server keeps track of which segments have already beendownloaded), RTP performs a push function where a server drives filetransfers. In RTP, a server must track status of a client device inorder to send data at correct times. In contrast, being stateless(server does not track which segments have already been downloaded),HTTP performs a pulling function where a client device drives filetransfers by requesting segments as needed. In HTTP a client devicesends a request to a server, upon receipt of which the server sendsdata, obviating need for the server to track client device status. Thisallows an HTTP transferring server to remain unaware of sessions, whichreduces the load on the server and provides ease of contentdistribution. Dynamic handling of fluctuating bandwidth can be difficultin RTP streaming without SVC or another scalable codec (see reference[5], incorporated by reference herein in its entirety). However, HTTPmultimedia transferring adds a significant overhead to a transferringsession compared to RTP (see reference [6], incorporated by referenceherein in its entirety).

Moreover, conventional HTTP approaches do not actually represent realstreaming. Instead, conventional HTTP “streaming” comprises progressivedownloading, i.e., downloading, combined with immediate playback. Whilesimple and deployable, progressive HTTP downloading does not managefluctuating bandwidth issues well. Dynamic Adaptive Streaming over HTTP(DASH) was developed to address bandwidth fluctuation in progressivedownloading.

DASH allows HTTP to bypass firewalls and NAT and its dynamic functionhandle varying bitrates. Essentially, DASH cuts media content intoindependently decodable segments. This allows encoding the media contentat different qualities or resolutions, while dividing the media contentinto segments of equal length. Client devices use HTTP to access themedia content and select the segments that most effectively fulfillclient devices' new bandwidth or resolution demands. DASH typically usesa manifest file (MF) that provides a description of the media contentand can be, for instance, extensible markup language (XML) based. Onrequest from a client device to a server, the manifest file can beprovided from the server to the client device to initiate a session. Theclient device can parse the manifest file and request individual mediacontent segments according to information found in the manifest file.

DASH system adaptation method (also referred to as adaptation logic) isgenerally located at the client side, which leverages client devices'awareness of their capabilities and bandwidth requirements. It can beassumed that DASH may become widely deployed over the internet andmobile networks in the next few years. Mobile networks are proliferatingrapidly, and video transferring is expected to comprise most trafficthereon over the next few years. However, neither HTTP nor the proxiesthat the protocol exploits to cache previously selected content (forbandwidth and cost conservation) are designed optimally for real timestreaming.

It may be assumed that virtually every HTTP connection uses a proxy thatis somewhere in the network, where a proxy is a network element that canstore content that has been previously selected by other users connectedto the internet through this proxy. For a DASH session, content is thusdistributed not simply by content providers on the CDN network, but isalso distributed in the network through the proxies. Distributionthrough the proxies is uncontrollable by the content providers becauseit depends on the client devices. For instance, distribution through theproxies may be significantly influenced by a client device's networklocation and capabilities. Most proxies thus cache only parts of thecontent (e.g., segments of media content of a certain bitrate,resolution, language classifications, or other characteristics by whichthey are cached).

Conventional DASH adaptation methods do not take this fact into account.As mobile networks and video transferring traffic thereon proliferate,this can impede optimum performance.

FIG. 1 depicts a basic representation of a DASH protocol where MF refersto a manifest file, DF refers to delivery format, ISOBMFF refers to afile format, and M2TS refers to a transport stream.

Proprietary solutions from various companies currently deployed in thisarea of technology include Microsoft's Smooth Streaming (see reference[8], incorporated by reference herein in its entirety), Adobe's DynamicHTTP Streaming (see reference [9], incorporated by reference herein inits entirety), and Apple's HTTP Live Streaming (see reference [10],incorporated by reference herein in its entirety). Also other consortiasuch as ISO/IEC MPEG (see reference [2], incorporated by referenceherein in its entirety) or 3GPP (see reference [7], incorporated byreference herein in its entirety) are currently trying to standardizethis technology.

Each of these systems can follow nearly the same architecture asdepicted in FIG. 1 and can utilize some kind of manifest file (MF). Themanifest file can provide a description of media content adapted to betransferred and is generally XML (extensible markup language) based. Onrequest, the manifest file can be provided to the client device in orderto initiate a session. The client can parse the manifest file andrequest individual segments compliant to a delivery format (DF) usingHTTP (or other protocols) and according to the information found in themanifest file. Consequently, in the present disclosure, the manifestfile can be referred to as an MPD (Media Presentation Description) andthe data model of this MPD is depicted in FIG. 2. The MPD can follow adata model comprising a sequence of one or more representations. Asingle representation can refer to a specific media having certaincharacteristics such as bitrate, resolution, or language. Furthermore,each representation may comprise one or more segments that describe themedia content and/or metadata to decode and present the included mediacontent.

The adaptation method (also referred to as adaptation logic) in such asystem is generally located at the client side, which can be beneficialbecause the client knows its capabilities and bandwidth requirementsbest. However, this technique can also introduce same drawbacks. Currentresearch (see references [1], [3], and [12]-[19], each of which isincorporated by reference herein in its entirety) is focused on oneclient device and how to properly adapt to this client device's needs toyield the best quality. New drawbacks may arise with increaseddeployment of adaptation methods such as DASH. For instance, mobilenetworks may be affected in the future because mobile data traffic maygrow by a factor of 40 between 2009 and 2014 as recent studies seem toindicate (see reference [11], incorporated by reference herein in itsentirety). Among mobile traffic, mobile video traffic may then accountfor approximately 66% of all mobile traffic.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more embodiments of thepresent disclosure and, together with the description of exampleembodiments, serve to explain the principles and implementations of thedisclosure.

FIG. 1 depicts a basic representation of dynamic adaptive streaming overHTTP (DASH) protocol.

FIG. 2 depicts a data model of a media presentation description.

FIG. 3 depicts an example scenario where multiple devices aretransferring media content.

FIG. 4 depicts an additional example scenario where multiple devices aretransferring media content.

FIGS. 5-7 provide flowcharts that depict adaptation algorithms ormethods.

DESCRIPTION OF EXAMPLE EMBODIMENTS

In an example embodiment of the invention, a quality level is selectedfrom among a plurality of quality levels of media content adapted to betransferred, each quality level being representative of a media contentversion, each media content version comprising a first plurality ofmedia content segments corresponding to time indices, wherein a secondplurality of media content segments is associated with equal or varyingquality levels and varying time indices and is adapted to be transferredto a client device with a buffer, further comprising: selecting a lowestquality level from among the plurality of quality levels if the bufferis not filled to a threshold level.

In an example embodiment of the invention, a quality level is selectedfrom among a plurality of quality levels of media content adapted to betransferred, each quality level being representative of a media contentversion, each media content version comprising a first plurality ofmedia content segments corresponding to time indices, wherein a secondplurality of media content segments is associated with equal or varyingquality levels and varying time indices and is adapted to be transferredto a client device with a buffer, further comprising: providing aquality level of a previously transferred media content segment; settingan intermediate quality level equal to a highest quality level supportedby available data rate of a network link; and selecting the intermediatequality level if such level is below the quality level of the previouslytransferred media content segment.

In an example embodiment of the invention, adjustment of quality levelof media content adapted to be transferred over a network link iscontrolled, the media content comprising a set of available mediacontent versions, each available media content version being associatedwith a quality level, wherein a plurality of media content segments isadapted to be transferred, each media content segment being associatedwith equal or varying quality levels and varying time indices, furthercomprising: providing a first quality level representative of apreviously transferred media content segment; providing a second qualitylevel, wherein the second quality level is selected from among qualitylevels representative of the set of available media content versions; A)if the second quality level is less than the first quality level:setting a next quality level equal to the second quality level, the nextquality level being representative of a next media content segmentadapted to be transferred; and applying a backoff time to transferringof the media content such that quality level of the media contentadapted to be transferred is prevented from increasing from the nextquality level until the backoff time has passed; B) else if the secondquality level is higher than the first quality level and the backofftime is less than or equal to zero: setting the next quality level equalto the second quality level.

In an example embodiment of the invention, adjustment of quality levelof media content adapted to be transferred over a network link iscontrolled, the media content comprising a set of available mediacontent versions, each available media content version being associatedwith a quality level, wherein a plurality of media content segments isadapted to be transferred, each media content segment being associatedwith equal or varying quality levels and varying time indices, furthercomprising: providing a first quality level representative of apreviously transferred media content segment; providing a second qualitylevel, wherein the second quality level is selected from among qualitylevels corresponding to the set of available media content versions;providing a counter variable; A) if the second quality level is lessthan the first quality level: setting a next quality level equal to thesecond quality level, the next quality level being representative of anext media content segment adapted to be transferred; B) else if thesecond quality level is higher than the first quality level and abackoff time is less than or equal to zero: determining whether or notthe network link can support the second quality level, wherein thedetermining comprises a function of network architecture of the networklink; a) if the network link can support the second quality level:setting the counter variable equal to zero; and setting the next qualitylevel equal to the second quality level; b) else: applying the backofftime to transferring of the media content such that quality level of themedia content adapted to be transferred is prevented from increasingfrom the next quality level until the backoff time has passed; andupdating the counter variable; C) else: setting the next quality levelequal to the first quality level.

In an example embodiment of the invention, adjustment of quality levelof media content adapted to be transferred over a network link iscontrolled, the media content comprising a set of available mediacontent versions, each available media content version being associatedwith a quality level, wherein a plurality of media content segments isadapted to be transferred, each media content segment being associatedwith equal or varying quality levels and varying time indices, andwherein a session of transferring media content is initiated bydownloading a media presentation description or a manifest file, furthercomprising: providing a first quality level representative of apreviously transferred media content segment; providing a second qualitylevel, wherein the second quality level is selected from among qualitylevels corresponding to the set of available media content versions; A)if the second quality level is less than the first quality level:setting a next quality level equal to the second quality level, the nextquality level being representative of a next media content segmentadapted to be transferred; B) else if the second quality level is higherthan the first quality level: determining a current client score basedon average peak-signal-to-noise-ratio and maximumpeak-signal-to-noise-ratio representative of all transferred mediacontent segments starting from initiation of the session up until a timeindex corresponding to the next media content segment; determining afuture client score based on the second quality level; a) if the futureclient score is greater than or equal to the current client score:determining whether or not the network link can support the secondquality level, wherein the determining comprises a function of networkarchitecture of the network link; i) if the network link can support thesecond quality level: setting the next quality level equal to the secondquality level; C) else: setting the next quality level equal to thefirst quality level.

In an example embodiment of the invention, a network adapted to transfermedia content is provided, comprising: one or more content-storagedevices that are configured to store the media content, the mediacontent comprising a set of available media content versions, eachavailable media content version being associated with a quality level,wherein a plurality of media content segments is adapted to betransferred, each media content segment being associated with equal orvarying quality levels and varying time indices; and one or more clientdevices that are configured to transfer the media content from the oneor more content-storage devices over a network link, the one or moreclient devices being further configured to: store a first quality levelrepresentative of a media content segment previously transferred fromthe one or more content-storage devices to the one or more clientdevices; store a second quality level, wherein the second quality levelis selected from among quality levels representative of the set of mediacontent versions available from the one or more content-storage devices;A) if the second quality level is less than the first quality level: seta next quality level equal to the second quality level, the next qualitylevel being represented of a next media content segment adapted to betransferred; and apply a backoff time to transferring of the mediacontent such that quality level of the media content adapted to betransferred is prevented from increasing from the next quality leveluntil the backoff time has passed; B) else if the second quality levelis higher than the first quality level and the backoff time is less thanor equal to zero: set the next quality level equal to the second qualitylevel.

In an example embodiment of the invention, a network adapted to transfermedia content is provided, comprising: one or more content-storagedevices that are configured to store the media content, the mediacontent comprising a set of available media content versions, eachavailable media content version being associated with a quality level,wherein a plurality of media content segments is adapted to betransferred, each media content segment being associated with equal orvarying quality levels and varying time indices; and one or more clientdevices that are configured to transfer the media content from the oneor more content-storage devices over a network link, the one or moreclient devices being further configured to: store a first quality levelrepresentative of a media content segment previously transferred fromthe one or more content-storage devices to the one or more clientdevices; store a second quality level, wherein the second quality levelis selected from among quality levels representative of the set of mediacontent versions available from the one or more content-storage devices;store a counter variable; A) if the second quality level is less thanthe first quality level: set a next quality level equal to the secondquality level, the next quality level being representative of a nextmedia content segment adapted to be transferred; B) else if the secondquality level is higher than the first quality level and a backoff timeis less than or equal to zero: determine whether or not the network linkcan support the second quality level, wherein the determining comprisesa function of network architecture of the network link; a) if thenetwork link can support the second quality level: set the countervariable equal to zero; and set the next quality level equal to thesecond quality level; b) else: apply the backoff time to transferring ofthe media content such that quality level of the media content adaptedto be transferred is prevented from increasing from the next qualitylevel until the backoff time has passed; and update the countervariable; C) else: set the next quality level equal to the first qualitylevel.

In an example embodiment of the invention, a network adapted to transfermedia content is provided, comprising: one or more content-storagedevices that are configured to store the media content, the mediacontent comprising a set of available media content versions, eachavailable media content version being associated with a quality level,wherein a plurality of media content segments is adapted to betransferred, each media content segment being associated with equal orvarying quality levels and varying time indices; and one or more clientdevices that are configured to transfer the media content from the oneor more content-storage devices over a network link, the one or moreclient devices being further configured to: store a first quality levelrepresentative of a media content segment previously transferred fromthe one or more content-storage devices to the one or more clientdevices; store a second quality level, wherein the second quality levelis selected from among quality levels representative of the set of mediacontent versions available from the one or more content-storage devices;A) if the second quality level is less than the first quality level: seta next quality level equal to the second quality level, the next qualitylevel being representative of a next media content segment adapted to betransferred; B) else if the second quality level is higher than thefirst quality level: determine a current client score based on averagepeak-signal-to-noise-ratio and maximum peak-signal-to-noise-ratiorepresentative of all transferred media content segments starting frominitiation of the session up until a time index corresponding to thenext media content segment; determine a future client score based on thesecond quality level; a) if the future client score is greater than orequal to the current client score: determine whether or not the networklink can support the second quality level, wherein the determiningcomprises a function of network architecture of the network link; i) ifthe network link can support the second quality level: set the nextquality level equal to the second quality level; C) else: set the nextquality level equal to the first quality level.

As used herein, the term “network link” may refer to a connectionbetween a client device (e.g., a mobile device, computer, tabletcomputer) and a source of media content (e.g., content-server, proxy). Aproxy can be utilized as an intermediary between the client device andthe content-server.

As used herein, the term “network architecture” may refer to specificconfiguration of content-servers, proxies, gateways, and client devicesin a network link.

As used herein, the term “content-storage device” may refer to a devicethat can store media content either temporarily (e.g., a proxy) orlong-term (e.g., a content-server).

As used herein, the term “proxy” may refer to a network element thatstores content that has been previously selected by one or more clientdevices that are connected to the internet through this proxy. Internetservice providers (ISP) and companies can use caching proxies to reducedownstream and upstream data rate usage and thus reduce cost.Distribution of content through the proxies depends on the clientdevices (e.g., location and/or available data rate of the clientdevices). Proxies generally cache a part of the content (e.g., somesegments of a given bitrate, resolution, language, and so forth).

As used herein, the term “media presentation description” (MPD) mayrefer to a manifest file (MF) describing media content. FIG. 2 depicts adata model of an exemplary MPD that comprises a sequence of one or morerepresentations. The MPD is provided by either a content-server or aproxy to a client device upon the client device's request in order toinitiate a transferring session.

As used herein, the term “representation” may refer to a set ofinformation referring to a portion of data which comprises specificmedia segments having certain characteristics. Characteristics of mediasegments include, by way of example and not of limitation, bitrate,resolution, camera angle, region of interest, presence of audio andquality of audio (if present), presence of video and quality of video(if present), codec (e.g., MPEG-2, AVC, MVC, SVC, and so forth), andlanguage. Furthermore, each representation comprises one or moresegments containing information that describes the media content and/ormetadata to decode and present the media content referred to by therepresentation.

As used herein, the term “current time index” may refer to a time indexcorresponding to a media content segment currently being transferred orabout to be transferred.

As used herein, the term “previously transferred segment” may refer to asegment of media content with a time index lower than the current timeindex, indicating media content which has already been transferred.

As used herein, the term “module” may refer to a unit that is configuredto perform certain functions. Modules may be implemented in hardware,software, firmware, or combination thereof.

As used herein, the term “media content version” may refer to a versionof media content comprising many segments and associated with a qualitylevel. The quality level requires a certain amount of available datarate in order to be transferred.

As used herein, the term “non-cacheable object” may refer to an HTTPobject where the “Cache-Control” feature is set to no-cache or anotheroption that disables caching (see reference [1]).

As used herein, the term “quality” may refer to both objectiveimage/video quality and subjective image/video quality. Objectiveimage/video quality generally can be quantified. Examples of measures of(objective) image/video quality include distortion between an expectedimage and a predicted image, signal-to-noise ratio (SNR) of an imagesignal, peak signal-to-noise ratio (PSNR) of an image signal, and soforth.

Subjective image/video quality may refer to the quality of the image asseen by a viewer of the image/video. Although subjective image/videoquality can also be measured using objective measures of image/videoquality, an increase in objective image/video quality does notnecessarily yield an increase in subjective image/video quality, andvice versa. In relation to images processed using block-basedoperations, for instance, subjective image/video quality considerationscan involve determining how to process pixels along block boundariessuch that perception of block artifacts are reduced in a final displayedimage. To an observer of an image, subjective quality measurements aremade based on evaluating features such as, but not limited to,smoothness, sharpness, details, and temporal continuity of variousfeatures in the image.

Quality may also refer to smoothness of media playback. For example, amedia session where playback repeatedly halts and then resumes (jolting)would exhibit low quality whereas a media session without jolting wouldexhibit high quality.

As used herein, the term “quality level” may include, by way of exampleand not of limitation, metrics such as bitrate, resolution, codec,language, presence of audio and quality of audio (if present), andpresence of video and quality of video (if present). By way of exampleand not of limitation, four different quality levels, each associatedwith an index, may be specified as follows:

Quality_level 1: only audio→bitrate=100 kbps

Quality_level 2: audio+low quality video→bitrate=500 kbps

Quality_level 3: audio+high quality video→bitrate=1000 kbps

Quality_level 4: audio+high quality video in highresolution→bitrate=2000 kbps.

In this example, note that quality levels whose indices differ by onewould be referred to as being one step removed from each other.Generally, adjacent quality levels, which are those with indices thatdiffer by one, differ in quality by a smallest step amount of change inquality. For example, quality levels 1 and 3 differ in quality by asmaller amount than a quality difference between quality levels 1 and 4.Allowed transitions between two quality levels can be set to be within adefined range at a given time instance. As one example, a condition canbe set such that quality levels can only transition between qualitylevels associated with adjacent indices at a given time instance. Asanother example, a condition can be set such that quality levels canonly transition between quality levels with a difference in index ofthree (or some other value) or less at a given time instance.

As used herein, the terms “bandwidth”, “data capacity”, and “availabledata rate” are used interchangeably and may refer to maximum rate ofdata throughput that a given link can carry.

As used herein, the phrase “supportable by the network link” may referto capability of a network link to transfer media content at a givenquality level for a duration of time spanning many media contentsegments without being forced to select a lower quality level.

As used herein, the term “streaming” may refer to transferring data,possibly followed by immediate playback.

As used herein, the term “transferring” may refer to moving data fromone location to another (e.g., from content-server to a client device)and may include streaming. Transferring can also refer to chunk-basedprogressive downloading.

As used herein, the term “adaptation method” may refer to a method forselecting media content versions to be transferred based on availabledata rate of a network link.

As used herein, the term “defensive adaptation methods” may refer tothose adaptation methods that do not react to short term throughputchanges and where transitions between different representations aregenerally performed in a step-wise manner. Step-wise can refer totransitioning between different quality levels without skippingintermediate quality levels. For example, if three quality levels (e.g.,500 Kbps, 1000 Kbps, 1800 Kbps) are available, a step-wise transitionmay refer to a transition from 500 Kbps to 1000 Kbps (or vice versa) butnot from 500 Kbps directly to 1800 Kbps (or vice versa).

As used herein, the term “aggressive adaptation methods” may refer tothose adaptation methods that do the opposite of defensive adaptationmethods. Aggressive adaptation methods may react to short termthroughput changes and transitions made by the aggressive adaptationmethods between different representations need not be step-wise.

It should be noted that while the present disclosure makes reference tobandwidth adaptation methods for transferring data over HTTP, theembodiments of the present disclosure can be utilized in otherprotocols. For example, the embodiments of the present disclosure can beutilized for protocols that utilize proxy caches with chunk-baseddynamic streaming and where adaptation logic is located at the clientside. Several embodiments of the present disclosure can be utilized toreduce adverse effects that may occur in a network system due topresence of a proxy between a content-server and a client device.

Two examples presented below depict problems of conventional DASHadaptation methods, which can impede optimal network performance. Bothexamples consider a scenario with multiple client devices transferringmedia content through a proxy, with media content available at differingquality levels depending on available data rate.

In a scenario depicted in FIG. 3, Devices A and B are currentlytransferring media content through a live DASH session over a network. Anetwork link between any two points (e.g., between a Content-Server anda client device such as Device A or B) is constrained by a link withinthe network link associated with a lowest available data rate (e.g.,between a client device and a Gateway). Consider an MPD that containsrepresentations describing different versions of the media content withbitrates of 500 Kbps (kilobits per second), 1000 Kbps, 1500 Kbps and3500 Kbps. Further, consider that links between Devices A and B andGateway 1 have a limited available data rate of 2000 Kbps. Links betweenGateways 1 and 2 to a Proxy each have an available data rate of 1 Gbps(gigabits per second) and therefore do not limit overall networkperformance. Devices A and B are transferring a version of media contentreferred to by the 1500 Kbps representation (hereafter referred to asthe 1500 Kbps media content version) because of their limited availabledata rate. The 1500 Kbps media content version will be cached on theProxy.

Consider that Device C joins the network after Devices A and B have beentransferring media content for some time. A link between theContent-Server and the Proxy can be (but need not be) split evenly ifGateways downstream from the Proxy are requesting different mediacontent versions. For purposes of discussion, such link is assumed tosplit evenly between Gateways which are simultaneously requestingdifferent media content versions. A link between Device C and Gateway 2has an available data rate of 4000 Kbps. Defensive adaptation methodsnormally select the lowest available bitrate representation at thebeginning of a session to fill a device's buffer. As a result, Device Cwill first begin transferring the 500 Kbps media content version andmeasure an available data rate of 2000 Kbps in Device C's link to theContent-Server because the link between the Content-Server and the Proxyhas an available data rate of 4000 Kbps and such available data rate isshared between the Gateways 1 and 2. Such sharing occurs because a linkbetween the Proxy and Gateway 1 is carrying a different media contentversion than a link between the Proxy and Gateway 2.

After Device C has measured an available data rate of 2000 Kbps, DeviceC will step up through the 1000 Kbps representation to the 1500 Kbpsrepresentation. The 1500 Kbps media content version is cached on theProxy and does not need to be downloaded from the Content-Server.Therefore, Device C will measure an available data rate of 4000 Kbps andswitch up to the 3500 Kbps representation. However, since the 3500 Kbpsmedia content version is not cached on the Proxy, the 3500 Kbps mediacontent version must be downloaded from the Content-Server. Device Cwill then measure an available data rate of 2000 Kbps (the 4000 Kbpslink between Content-Server and Proxy is split equally between Gateways1 and 2) and switch down to the 1500 Kbps representation. As a result,Device C will switch between downloading the 1500 Kbps and 3500 Kbpsmedia content versions throughout the entire session.

Frequent switching between different media content versions caninfluence quality of experience (QoE). Transitions between qualitylevels associated with a larger difference in quality of media contentversion to be transferred can influence quality of experience more thantransitions between quality levels associated with a smaller differencein quality of media content version to be transferred. For instance,transitions between 1000 Kbps and 3500 Kbps generally influence qualityof experience more than transitions between 1000 Kbps and 1500 Kbps.Furthermore, video buffer of Device C may run out of frames duringdownload of segments from the 3500 Kbps media content version, becausethe available data rate over the network link to Device C isinsufficient for the 3500 Kbps media content version, which generallyleads to a session that is not smooth and would thus be associated witha decrease in quality of experience (relative to a smooth session) atDevice C.

A scenario depicted in FIG. 4 is similar to the scenario depicted inFIG. 3 with modified conditions and a different MPD. The MPD containsrepresentations referring to media content versions with bitrates of 500Kbps, 1000 Kbps, 2000 Kbps, 3000 Kbps, and 4000 Kbps. Links betweenDevices A and B to Gateway 1 have an available data rate of 3500 Kbps.Links between Gateways 1 and 2 to a Proxy each have an available datarate of 1 Gbps and therefore do not limit overall network performance.Devices A and B are transferring a live DASH session and have selectedthe 3000 Kbps representation due to their limited available data rate tothe Proxy. Device C joins the network later, with a link to Gateway 2having an available data rate of 5000 Kbps, and selects the 500 Kbpsrepresentation to fill its buffer as fast as possible. The link betweenthe Proxy and the Content-Server will now be shared between Gateway 1servicing Devices A and B and Gateway 2 servicing Device C.

Both Gateways would each be assigned 2500 Kbps of the link capacity of5000 Kbps between the Content-Server and the Proxy if the link wereshared equally. This means that Devices A and B can no longer transferthe 3000 Kbps media content version. Therefore, because of the newnetwork conditions, Devices A and B switch down to a lower bitraterepresentation and corresponding media content version. This switch downgenerally results in both Devices A and B transferring the 2000 Kbpsmedia content version, because this media content version is the bestfit for the network conditions of these two devices, where the phrase“best fit for the network conditions” refers to selection of a highestquality media content version available that can be transferred at adata rate defined by network conditions. The length of time required forDevices A and B to arrive at a state where both are transferring the2000 Kbps media content version depends on the adaptation method.

In the meantime, Device C will fill its buffer and switch up to the 2000Kbps representation after some time dependent on adaptation method usedby Device C. When Device C selects the 2000 Kbps representation, DeviceC will measure an available data rate of 5000 Kbps because the 2000 Kbpsmedia content version should be cached on the Proxy (because of DevicesA and B have already requested the 2000 Kbps media content version).After Device C selects the 2000 Kbps representation, the connectionbetween the Proxy and the Content-Server will no longer be shared. Thismeans that Device A and B will measure an available data rate of 3500Kbps and Device C will measure an available data rate of 5000 Kbpsbecause all three devices now transfer the same 2000 Kbps media contentversion stored on the Proxy.

Since Devices A and B measure an available data rate of 3500 Kbps,Devices A and B will then switch to the 3000 Kbps representation. Also,since Device C measures an available data rate of 5000 Kbps, Device Chas two switch up options. Defensive adaptation methods would select the3000 Kbps representation and aggressive adaptation methods would selectthe 4000 Kbps representation.

However, both options would end at the same representation.Specifically, after a period of time, Device C will select the 4000 Kbpsrepresentation regardless of whether defensive or aggressive adaptationmethods were used. The defensive adaptation method would first selectthe 3000 Kbps representation and measure an available data rate of 5000Kbps because the 3000 Kbps media content version is cached on the Proxyand all devices are currently transferring the 3000 Kbps media contentversion. Subsequently, Device C would select the 4000 Kbpsrepresentation and measure an available data rate of 2500 Kbps becausethe 4000 Kbps media content version is not cached on the Proxy. Thisswitch-up decision by Device C will also affect Devices A and B becauseDevices A and B will now measure an available data rate of 2500 Kbps andthe whole adaptation process starts again.

The above scenario shows that an adaptation decision by one clientdevice (e.g., Device C) can adversely influence other client devices(e.g., Devices A and B). Device C will constantly switch between the2000 Kbps, 3000 Kbps, and 4000 Kbps representations and eventually alsoexhaust its video buffer and produce a jolting session, which decreasesQoE at Device C. In addition, Device C's adaptation decisions alsoinfluence Devices A and B. Specifically, both Devices A and B willswitch between the 2000 Kbps and 3000 Kbps representations during thewhole session and both could also exhaust their video buffers due tonetwork condition changes introduced by Device C. Consequently, QoE ofthe three client devices will be reduced.

As demonstrated by the preceding two scenarios, bandwidth adaptationmethods may only estimate available data rate from received packetsdirectly and may not necessarily consider the network architecture(e.g., including content-server, proxy, gateways, and client devices).This may cause frequent representation (and corresponding media contentversion) switching and jolting playback at one device, which may degradeQoE as depicted in the preceding two scenarios. Moreover, due to theswitching at this one device, other devices' sessions can be influenced,e.g., jolting playback and frequent representation (and correspondingmedia content version) switching, thus degrading QoE of these otherdevices in the network.

Proxy aware adaptation can address these issues and balance bandwidthsharing among peers. As previously described, some bandwidth adaptationmethods may not consider uncontrolled media distribution through proxycaches. Therefore, these bandwidth adaptation methods may not take intoaccount that bandwidth fluctuations can be caused by a client device'sown unfavorable adaptation decisions. Bandwidth adaptation methodsprovided in this disclosure try to influence the adaptation process in away that the previously described issues can be avoided. Proxy awareadaptation can be utilized to balance maximum overall quality and allowfor smooth media playback with fewer representation changes in a giventime period.

Table 1 defines some parameters for use in describing adaptationalgorithms. In the disclosure, metrics, client score and system score,defined by average PSNR of a session and the variance of the PSNR, canbe used as a measure of quality of the session.

TABLE 1 Parameters i ϵ [0, N] segment index k ϵ [1, M ] device indexμ_(i) average PSNR of segment i μ_(k) average PSNR at device k f (i)representation PSNR of the segment i, f(0) is equal to the PSNR atstartup delay period t_(i) length of segment i t_(n) length of thesession

The average PSNR at the device k is defined as μ_(k):

$\begin{matrix}{\mu_{session} = {\frac{1}{M}{\sum\limits_{k = 1}^{M}\mu_{k}}}} & (1)\end{matrix}$

The average PSNR of the session over all M devices is defined asμ_(session):

$\begin{matrix}{\mu_{session} = {\frac{1}{M}{\sum\limits_{k = 1}^{M}\mu_{k}}}} & (2)\end{matrix}$

The variance of PSNR at the device k is defined as σ_(k) ²:

$\begin{matrix}{{g\left( \mu_{i} \right)} = \left\{ {{\begin{matrix}1 & {{{if}\mspace{14mu} i} = 0} \\1 & {{{if}\mspace{14mu} {f(i)}} \neq {f\left( {i - 1} \right)}} \\0 & {others}\end{matrix}\sigma_{k}^{2}} = {\frac{1}{t_{n}}{\sum\limits_{i = 0}^{N}{{g\left( \mu_{i} \right)}*\left( {{f(i)} - \mu_{k}} \right)^{2}}}}} \right.} & (3)\end{matrix}$

Standard deviation of the PSNR at the device k can be given by:

σ_(k)=√{square root over (σ_(k) ²)}

The coefficient of variation at the device k is defined as cν_(k):

${cv}_{k} = \frac{\sigma_{k}}{\mu_{k}}$

where the coefficient of variation is a dimensionless number that can beused to compare sessions with different means.

The coefficient of variation at the session is defined as cν_(session):

$\begin{matrix}{{cv}_{session} = {\frac{1}{M}{\sum\limits_{k = 1}^{M}{cv}_{k}}}} & (4)\end{matrix}$

The client and system score are defined in (5) and (6), respectively:

$\begin{matrix}{{client\_ score}_{bandwidth} = \frac{\mu_{k}}{{PSNR}_{{ma}\; x}*\alpha*e^{\beta*{cv}_{k}}}} & (5) \\{{system\_ score}_{bandwidth} = \frac{\mu_{session}}{{PSNR}_{{ma}\; x}*\alpha*e^{\beta*{cv}_{session}}}} & (6)\end{matrix}$

where PSNR_(max) is the maximum PSNR at the device over all segmentsthat are being downloaded and α and β are weighting factors utilized toadjust influence of variance since variance depends on human perception.

Different adaptation methods can be compared through computation of aclient score or a system score when the adaptation methods underconsideration are implemented. In general, an adaptation methodassociated with higher client and/or system scores may be considered tobe a better method given network conditions. It is noted that Equations(5) and (6) comprise exemplary equations for computing the client scoreand system score, respectively, and need not be exponential functions.By way of example and not of limitation, client and system scores can becomputed using linear functions or square functions.

In this disclosure, several embodiments of bandwidth adaptationalgorithms are described.

An embodiment of an adaptation algorithm uses exponential backoff. Thisalgorithm decreases number of switch up points if a switch down occurs.Specifically, the exponential backoff provides a wait time before aclient device is allowed to switch up again after switching down. Foreach segment, a client device makes a decision regarding which qualitylevel (e.g., bitrate, resolution, and so forth) should be chosen basedon previously measured available data rate of the network link. If theclient device detects that there is currently not enough available datarate on the network link for the representation that is beingtransferred, the client device will switch down to a representation thatdoes not exceed the available data rate of the network link. This switchdown decision will result in application of an exponential backoff tothe client device. Therefore, the exponential backoff reduces frequentrepresentation switching and thus may reduce negative influence on othersessions. This adaptation algorithm does not differentiate betweenexternal available data rate fluctuations due to the uncontrolleddistribution of media through proxy caches and fluctuations caused bythe client device.

The following algorithm provided below, corresponding to the algorithmdescribed in the immediately preceding paragraphs, returns whichavailable quality level (e.g., bitrate or resolution) should be used forthe next segment, which, in turn, determines which representation shouldbe selected from available representation options. Availablerepresentation options provide information describing available mediacontent versions, each available media content version being associatedwith a quality level. Different media content versions may have the samequality level (e.g., bitrate or resolution), but differ in othercharacteristics (e.g., language). Different media content versions mayalso have higher or lower quality levels. For instance, othercharacteristics being equal, a media content version with a higherresolution is generally considered to be at a higher quality level thana media content version with a lower resolution.

The backoff function, which can be given by αe^((β)*^(count)) asdiscussed below, can be adjusted with parameters α and β either in alinear manner or a nonlinear manner, respectively. Note that α and βutilized in the backoff function are not the same as α and β inEquations (5) and (6) for computing client and system scores.Additionally, parameters γ and δ (also shown below) can be increased toaccelerate or decelerate the adaptation process, respectively. By way ofexample and not of limitation, all four parameters may be set equalto 1. In general, selection of these four parameters will depend onnetwork conditions. For mobile networks with high bandwidthfluctuations, for instance, β can be set equal to 0. Note that thisalgorithm can utilize information pertaining to quality level ofpreviously transferred media segments. Such information can be recordedfor use in the algorithm. A flowchart corresponding to this algorithm isdepicted in FIG. 5.

quality_level = low if buffer_fill_state>=min_buffer if backoff> 0backoff = backoff − γ endif for current_quality_level = low to high doif current_quality_level<measured_bandwidth quality_level =current_quality_level endif current_quality_level++ endfor ifquality_level<quality_level_of_chunk_before backoff = α *e^((β * count)) count = count + δ return quality_level elseif backoff<=0return quality_level endif quality_level = quality_level_of_chunk_beforeendif return quality_level

It should be noted that, based on the algorithm provided, exponentialbackoff can be cast as linear backoff. In the above pseudocode, if β isset equal to zero, then backoff is set by α (i.e., αe^((β)*^(count))=α).Additionally, offsets may be used in computing backoff such that backoffcan be provided by backoff=α*e^((β)*^(count+offset1))+offset2.

Aside from linear and exponential functions, other functions such aspolynomial functions (e.g., square, cubic) can also be used forcomputing backoff. Selection of a function can depend on applications,network conditions, and network infrastructures. For instance, a networkassociated with fewer fluctuations in network conditions, where networkconditions can comprise measured available data rate, may utilize afunction that increases faster with increasing number of switch-downs(and vice versa for a network associated with more fluctuations innetwork conditions). Some network statistics may be amenable to anexponential backoff function. Incorporating parameters (e.g., offset1,offset2) and/or selecting different functions (e.g., linear, square)increase configurability of the backoff function.

An additional embodiment of the present disclosure uses exponentialbackoff in addition to a probe function, where the probe function can beused to determine if available data rate of a network link is sufficientfor a given representation. In comparison to the first algorithm, asecond adaptation algorithm utilizes a different technique to reducebandwidth fluctuations caused by a client device switchingrepresentations.

As described in the first adaptation algorithm, bandwidth fluctuationscan be introduced due to bandwidth adaptation methods that do notconsider the uncontrolled distribution of media through proxy caches.The second adaptation algorithm uses a function referred to as probe toassist the client device in deciding whether or not to switch up to arepresentation requiring higher available data rate. This means thatadaptation decisions that lead to a switch up can be double checkedbased on information from the probe function. Specifically, adetermination is made as to whether or not sufficient available datarate exists on the network link for the purpose of transferring arepresentation under consideration suggested based on quality level of apreviously transferred media segment.

An input to the probe function is the quality level that should beprobed (e.g., a quality level associated with a segment from a givenrepresentation). The probe function returns a boolean value thatindicates if enough available data rate exists for the givenrepresentation. Exemplary techniques are provided for making such adetermination.

A first exemplary technique is that the server can provide anon-cacheable object. Therefore, available data rate of the network linkto the server can be estimated, for instance, by dividing size of thenon-cacheable object by time involved in completing transfer of thenon-cacheable object. Furthermore, based on the estimation, anapproximate determination can be made as to whether enough availabledata rate exists for a given representation.

A second exemplary technique is that the client device can download thefirst few bytes or a random byte range of a next segment of a mediacontent version associated with a given representation and make anapproximate determination as to whether there is enough available datarate for a given representation. Other estimation techniques of theavailable data rate can be used.

A third exemplary technique is that the proxy can modify the MPD andremove representations that cannot be used due to available data ratelimitations of the network link. A carrier network may instruct a proxyspecifically to modify the MPD so as to restrict representations madeavailable to a client device. Such restrictions may be applied, forinstance, to ensure bandwidth is available for additions to the networkin the future. The client devices are informed if the available datarate of the network link changes. This can be done with an updateinterval element inside of the MPD (e.g., all the client devices have toupdate the MPD in a given interval). Such updating can assist the clientdevice in periodically applying the latest changes to the MPD. Forexample, the MPD may be configured to instruct the client device toupdate (based on changes to the MPD made by the proxy) the clientdevice's local copy of the MPD every few seconds such as every 2 secondsor 10 seconds. The third exemplary technique can be utilized alternativeto or in conjunction with the probe function.

A fourth exemplary technique is that the proxy can offer a service thatprovides information about available data rate of the network link.Therefore, the client devices can request this service and gatherinformation about the available data rate.

The first, second, and fourth exemplary techniques are examples of aclient device initiated probe function, while third exemplary techniqueis an example of a proxy action which can yield results similar to aprobe function. The following algorithm, corresponding to the adaptationmethod of the preceding paragraphs, uses the probe function to determinean appropriate quality level for downloading media. A flowchartcorresponding to this algorithm is depicted in FIG. 6.

quality_level = low if buffer_fill_state>=min_buffer if backoff>0backoff = backoff − γ endif for current_quality_level = low to high doif current_quality_level<measured_bandwidth quality_level =current_quality_level endif current_quality_level++ endfor ifquality_level<=quality_level_of_chunk_before return quality_level elseifbackoff<=0 if probe(quality_level) count = 0 return quality_level elsebackoff = α * e^((β * count)) count = count + δ endelse endifquality_level=quality_level_of_chunk_before endif return quality_level

A further embodiment of an adaptation method utilizes functions inconjunction with or alternative to exponential backoff. These functionsare a calcCurrentScore function, which calculates a current client scorebased on the metric described in Equation (5), and acalcFutureEstimatedScore function, which will be described in the nextparagraph.

The calcFutureEstimatedScore function is also based on the metricdescribed in Equation (5). A difference between thecalcFutureEstimatedScore function and the calcCurrentScore function isthat the input values for the calcFutureEstimatedScore function, μ_(k)and cν_(k), are estimated based on observed network conditions or thevariance σ_(k) ². Therefore, it is possible to identify switch up pointswhich do not necessarily degrade network performance. For example, theclient device can estimate how long the client device will be able totransfer a media content version associated with a given representationunder consideration until a switch down occurs, where the givenrepresentation is selected in order to increase the client score asdescribed in Equation (5). Based on estimation of time during which aselected media content version can be transferred given networkavailable data rate limitations, it can be determined if a switch updecision under consideration will not necessarily degrade networkperformance.

The following algorithm, in accordance with the adaptation methoddescribed in the preceding paragraphs, determines an appropriate qualitylevel for transferring media content. A flowchart corresponding to thisalgorithm is depicted in FIG. 7.

quality_level = low if buffer_fill_state>=min_buffer forcurrent_quality_level = low to high do ifcurrent_quality_level<measured_bandwidth quality_level =current_quality_level endif current_quality_level++ endfor ifquality_level <= quality_level_of_chunk_before return quality_level elseclient_score = calcCurrentScore( ) client_score_future =calcFutureEstimatedScore(quality_level) if client_score_future>=client_score if probe(quality_level) return quality_level endif endifendif quality_level = quality_level_of_chunk_before endif returnquality_level

The examples set forth above are provided to give those of ordinaryskill in the art a complete disclosure and description of how to makeand use the embodiments of the bandwidth adaptation for dynamic adaptivetransferring of multimedia of the disclosure, and are not intended tolimit the scope of what the inventors regard as their disclosure.Modifications of the above-described modes for carrying out thedisclosure can be used by persons of skill in the art, and are intendedto be within the scope of the following claims.

Modifications of the above-described modes for carrying out the methodsand systems herein disclosed that are obvious to persons of skill in theart are intended to be within the scope of the following claims. Allpatents and publications mentioned in the specification are indicativeof the levels of skill of those skilled in the art to which thedisclosure pertains. All references cited in this disclosure areincorporated by reference to the same extent as if each reference hadbeen incorporated by reference in its entirety individually.

It is to be understood that the disclosure is not limited to particularmethods or systems, which can, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting. As used in this specification and the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontent clearly dictates otherwise. The term “plurality” includes two ormore referents unless the content clearly dictates otherwise. Unlessdefined otherwise, all technical and scientific terms used herein havethe same meaning as commonly understood by one of ordinary skill in theart to which the disclosure pertains.

The methods and systems described in the present disclosure may beimplemented in hardware, software, firmware or combination thereof.Features described as blocks, modules or components may be implementedtogether (e.g., in a logic device such as an integrated logic device) orseparately (e.g., as separate connected logic devices). The softwareportion of the methods of the present disclosure may comprise acomputer-readable medium which comprises instructions that, whenexecuted, perform, at least in part, the described methods. Thecomputer-readable medium may comprise, for example, a random accessmemory (RAM) and/or a read-only memory (ROM). The instructions may beexecuted by a processor (e.g., a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), or a field programmablegate array (FPGA)).

A number of embodiments of the disclosure have been described.Nevertheless, it will be understood that various modifications can bemade without departing from the spirit and scope of the presentdisclosure. Accordingly, other embodiments are within the scope of thefollowing claims.

Enumerated example embodiments (“EEEs”) of the present invention havebeen described above. However, an embodiment of the present inventioncan relate to one or more of the examples, enumerated in Table 2 below.

TABLE 2 Enumerated Example Embodiments 1. A method for selecting aquality level from among a plurality of quality levels of media contentadapted to be transferred, each quality level being representative of amedia content version, each media content version comprising a firstplurality of media content segments corresponding to time indices,wherein a second plurality of media content segments is associated withequal or varying quality levels and varying time indices and is adaptedto be transferred to a client device with a buffer, the methodcomprising: selecting a lowest quality level from among the plurality ofquality levels if the buffer is not filled to a threshold level. 2. Amethod for selecting a quality level from among a plurality of qualitylevels of media content adapted to be transferred, each quality levelbeing representative of a media content version, each media contentversion comprising a first plurality of media content segmentscorresponding to time indices, wherein a second plurality of mediacontent segments is associated with equal or varying quality levels andvarying time indices and is adapted to be transferred to a client devicewith a buffer, the method comprising: providing a quality level of apreviously transferred media content segment; setting an intermediatequality level equal to a highest quality level supported by availabledata rate of a network link; and selecting the intermediate qualitylevel if such level is below the quality level of the previouslytransferred media content segment. 3. A method for controllingadjustment of quality level of media content adapted to be transferredover a network link, the media content comprising a set of availablemedia content versions, each available media content version beingassociated with a quality level, wherein a plurality of media contentsegments is adapted to be transferred, each media content segment beingassociated with equal or varying quality levels and varying timeindices, the method comprising: providing a first quality levelrepresentative of a previously transferred media content segment;providing a second quality level, wherein the second quality level isselected from among quality levels representative of the set ofavailable media content versions; A) if the second quality level is lessthan the first quality level: setting a next quality level equal to thesecond quality level, the next quality level being representative of anext media content segment adapted to be transferred; and applying abackoff time to transferring of the media content such that qualitylevel of the media content adapted to be transferred is prevented fromincreasing from the next quality level until the backoff time haspassed; B) else if the second quality level is higher than the firstquality level and the backoff time is less than or equal to zero:setting the next quality level equal to the second quality level. 4. Themethod of EEE Error! Reference source not found., wherein the backofftime is provided by a linear, polynomial, or exponential function of oneor more scalar parameters. 5. The method of any one of EEEs Error!Reference source not found, or Error! Reference source not found.,wherein the backoff time comprises a function of number of times, upuntil a time index t_(c), that the second quality level has been lessthan the first quality level, wherein t_(c) comprises a time indexcorresponding to the next media content segment adapted to betransferred. 6. The method of any one of EEEs Error! Reference sourcenot found.-Error! Reference source not found., wherein the backoff timecomprises an integer. 7. The method of any one of EEEs Error! Referencesource not found.-Error! Reference source not found., further comprisingupdating the backoff time subsequent to transferring of the next mediacontent segment. 8. The method of EEE Error! Reference source notfound., wherein the updating the backoff time comprises: providing adecrementing parameter γ; if the backoff time is greater than zero:subtracting the decrementing parameter γ from the backoff time; andassigning a result of the subtracting to the backoff time. 9. The methodof EEE Error! Reference source not found., wherein the decrementingparameter γ comprises a constant or a variable. 10. The method of anyone of EEEs Error! Reference source not found.-Error! Reference sourcenot found., further comprising, subsequent to the updating: i) if thesecond quality level is greater than the first quality level and thebackoff time is less than or equal to zero: setting the next qualitylevel equal to the second quality level; ii) else: setting the nextquality level equal to the first quality level. 11. A method forcontrolling adjustment of quality level of media content adapted to betransferred over a network link, the media content comprising a set ofavailable media content versions, each available media content versionbeing associated with a quality level, wherein a plurality of mediacontent segments is adapted to be transferred, each media contentsegment being associated with equal or varying quality levels andvarying time indices, the method comprising: providing a first qualitylevel representative of a previously transferred media content segment;providing a second quality level, wherein the second quality level isselected from among quality levels corresponding to the set of availablemedia content versions; providing a counter variable; A) if the secondquality level is less than the first quality level: setting a nextquality level equal to the second quality level, the next quality levelbeing representative of a next media content segment adapted to betransferred; B) else if the second quality level is higher than thefirst quality level and a backoff time is less than or equal to zero:determining whether or not the network link can support the secondquality level, wherein the determining comprises a function of networkarchitecture of the network link; a) if the network link can support thesecond quality level: setting the counter variable equal to zero; andsetting the next quality level equal to the second quality level; b)else: applying the backoff time to transferring of the media contentsuch that quality level of the media content adapted to be transferredis prevented from increasing from the next quality level until thebackoff time has passed; and updating the counter variable; C) else:setting the next quality level equal to the first quality level. 12. Themethod of EEE Error! Reference source not found., wherein the updatingthe counter variable comprises incrementing the counter variable. 13.The method of any one of EEEs Error! Reference source not found, orError! Reference source not found., wherein the updating the countervariable comprises adding a constant value to the counter variable. 14.The method of any one of EEEs Error! Reference source not found.-Error!Reference source not found., wherein the determining whether or not thenetwork link can support the second quality level comprises:transferring a non-cacheable object from a content-server to a clientdevice of the network; estimating available data rate based on thetransferring; and determining whether or not enough available date rateexists for transferring media content over the network link at thesecond quality level. 15. The method of EEE Error! Reference source notfound., wherein the estimating comprises: dividing amount of datatransferred by time required for the transferring. 16. The method of anyone of EEEs Error! Reference source not found.-Error! Reference sourcenot found., wherein the determining whether or not the network link cansupport the second quality level comprises: transferring to a clientdevice a byte range from the next media content segment; estimatingavailable data rate based on the transferring; and determining whetheror not enough available date rate exists for transferring media contentover the network link at the second quality level. 17. The method of EEEError! Reference source not found., wherein the estimating comprises:dividing amount of data transferred by time required for thetransferring. 18. The method of any one of EEEs Error! Reference sourcenot found.-Error! Reference source not found., wherein the determiningwhether or not the network link can support the second quality levelcomprises: modifying a media presentation description or manifest fileto remove representations corresponding to media content versions notsupportable due to limitations in available data rate of the networklink, wherein the modifying is performed by a proxy of the network link,and wherein the media presentation description or manifest file providesinformation describing the set of available media content versions,wherein: i) if a representation corresponding to the second qualitylevel still exists in the media presentation description or manifestfile subsequent to the modifying: determining that the network link cansupport the second quality level; ii) else: determining that the networklink cannot support the second quality level. 19. The method of any oneof EEEs Error! Reference source not found.-Error! Reference source notfound., wherein the determining is based on information about availabledata rate of the network link, the information being provided by a proxyof the network link. 20. The method of any one of EEEs Error! Referencesource not found.-Error! Reference source not found., wherein thebackoff time is provided by a linear, polynomial, or exponentialfunction of one or more scalar parameters. 21. The method of any one ofEEEs Error! Reference source not found.-Error! Reference source notfound., wherein the backoff time comprises a function of the countervariable. 22. The method of any one of EEEs Error! Reference source notfound.-Error! Reference source not found., wherein the backoff timecomprises an integer. 23. The method of any one of EEEs Error! Referencesource not found.-Error! Reference source not found., further comprisingupdating the backoff time subsequent to transferring of the next mediacontent segment. 24. The method of EEE Error! Reference source notfound., wherein the updating the backoff time comprises: providing adecrementing parameter γ; if the backoff time is greater than zero:subtracting the decrementing parameter γ from the backoff time; andassigning a result of the subtracting to the backoff time. 25. Themethod of EEE Error! Reference source not found., wherein thedecrementing parameter γ comprises a constant or a variable. 26. Amethod for controlling adjustment of quality level of media contentadapted to be transferred over a network link, the media contentcomprising a set of available media content versions, each availablemedia content version being associated with a quality level, wherein aplurality of media content segments is adapted to be transferred, eachmedia content segment being associated with equal or varying qualitylevels and varying time indices, and wherein a session of transferringmedia content is initiated by downloading a media presentationdescription or a manifest file, the method comprising: providing a firstquality level representative of a previously transferred media contentsegment; providing a second quality level, wherein the second qualitylevel is selected from among quality levels corresponding to the set ofavailable media content versions; A) if the second quality level is lessthan the first quality level: setting a next quality level equal to thesecond quality level, the next quality level being representative of anext media content segment adapted to be transferred; B) else if thesecond quality level is higher than the first quality level: determininga current client score based on average peak-signal-to-noise-ratio andmaximum peak- signal-to-noise-ratio representative of all transferredmedia content segments starting from initiation of the session up untila time index corresponding to the next media content segment;determining a future client score based on the second quality level; a)if the future client score is greater than or equal to the currentclient score: determining whether or not the network link can supportthe second quality level, wherein the determining comprises a functionof network architecture of the network link; i) if the network link cansupport the second quality level: setting the next quality level equalto the second quality level; C) else: setting the next quality levelequal to the first quality level. 27. The method of EEE 26, wherein thedetermining whether or not the network link can support the secondquality level comprises: transferring a non-cacheable object from acontent-server to a client device of the network; estimating availabledata rate based on the transferring; and determining whether or notenough available date rate exists for transferring media content overthe network link at the second quality level. 28. The method of EEE 27,wherein the estimating comprises: dividing amount of data transferred bytime required for the transferring. 29. The method of EEE 26, whereinthe determining whether or not the network link can support the secondquality level comprises: transferring to a client device a byte rangefrom the next media content segment; estimating available data ratebased on the transferring; and determining whether or not enoughavailable date rate exists for transferring media content over thenetwork link at the second quality level. 30. The method of EEE 29,wherein the estimating comprises: dividing amount of data transferred bytime required for the transferring. 3E The method of EEE 26, wherein thedetermining whether or not the network link can support the secondquality level comprises: modifying a media presentation description ormanifest file to remove representations corresponding to media contentversions not supportable due to limitations in available data rate ofthe network link, wherein the modifying is performed by a proxy of thenetwork link, wherein the media presentation description or manifestfile provides information describing the set of available media contentversions, wherein: i) if a representation corresponding to the secondquality level still exists in the presentation description or manifestfile subsequent to the modifying: determining that the network link cansupport the second quality level; ii) else: determining that the networklink cannot support the second quality level. 32. The method of EEE 26,wherein the determining is based on information about available datarate of the network link, the information being provided by a proxy ofthe network link. 33. The method of any one of EEEs 3-32, wherein: thesecond quality level is the highest quality level corresponding tomeasured available data rate of the network link, wherein measurement ofthe available data rate assumes the media content is adapted to betransferred directly from a content-server, and the highest qualitylevel is selected from among quality levels corresponding to the set ofavailable media content versions. 34. The method of any one of EEEs3-33, wherein the plurality of quality levels is divided into steps,each quality level being associated with an index, and wherein adifference between an index associated with the second quality level andan index associated with the first quality level is within a set range.35. The method of any one of EEEs 3-33, wherein the plurality of qualitylevels is divided into steps, each quality level being associated withan index, and wherein an index associated with the second quality leveldiffers from an index associated with the first quality level by one.36. A network adapted to transfer media content, comprising: one or morecontent-storage devices that are configured to store the media content,the media content comprising a set of available media content versions,each available media content version being associated with a qualitylevel, wherein a plurality of media content segments is adapted to betransferred, each media content segment being associated with equal orvarying quality levels and varying time indices; and one or more clientdevices that are configured to transfer the media content from the oneor more content-storage devices over a network link, the one or moreclient devices being further configured to: store a first quality levelrepresentative of a media content segment previously transferred fromthe one or more content-storage devices to the one or more clientdevices; store a second quality level, wherein the second quality levelis selected from among quality levels representative of the set of mediacontent versions available from the one or more content- storagedevices; A) if the second quality level is less than the first qualitylevel: set a next quality level equal to the second quality level, thenext quality level being represented of a next media content segmentadapted to be transferred; and apply a backoff time to transferring ofthe media content such that quality level of the media content adaptedto be transferred is prevented from increasing from the next qualitylevel until the backoff time has passed; B) else if the second qualitylevel is higher than the first quality level and the backoff time isless than or equal to zero: set the next quality level equal to thesecond quality level. 37. A network adapted to transfer media content,comprising: one or more content-storage devices that are configured tostore the media content, the media content comprising a set of availablemedia content versions, each available media content version beingassociated with a quality level, wherein a plurality of media contentsegments is adapted to be transferred, each media content segment beingassociated with equal or varying quality levels and varying timeindices; and one or more client devices that are configured to transferthe media content from the one or more content-storage devices over anetwork link, the one or more client devices being further configuredto: store a first quality level representative of a media contentsegment previously transferred from the one or more content-storagedevices to the one or more client devices; store a second quality level,wherein the second quality level is selected from among quality levelsrepresentative of the set of media content versions available from theone or more content- storage devices; store a counter variable; A) ifthe second quality level is less than the first quality level: set anext quality level equal to the second quality level, the next qualitylevel being representative of a next media content segment adapted to betransferred; B) else if the second quality level is higher than thefirst quality level and a backoff time is less than or equal to zero:determine whether or not the network link can support the second qualitylevel, wherein the determining comprises a function of networkarchitecture of the network link; a) if the network link can support thesecond quality level: set the counter variable equal to zero; and setthe next quality level equal to the second quality level; b) else: applythe backoff time to transferring of the media content such that qualitylevel of the media content adapted to be transferred is prevented fromincreasing from the next quality level until the backoff time haspassed; and update the counter variable; C) else: set the next qualitylevel equal to the first quality level. 38. A network adapted totransfer media content, comprising: one or more content-storage devicesthat are configured to store the media content, the media contentcomprising a set of available media content versions, each availablemedia content version being associated with a quality level, wherein aplurality of media content segments is adapted to be transferred, eachmedia content segment being associated with equal or varying qualitylevels and varying time indices; and one or more client devices that areconfigured to transfer the media content from the one or morecontent-storage devices over a network link, the one or more clientdevices being further configured to: store a first quality levelrepresentative of a media content segment previously transferred fromthe one or more content-storage devices to the one or more clientdevices; store a second quality level, wherein the second quality levelis selected from among quality levels representative of the set of mediacontent versions available from the one or more content- storagedevices; A) if the second quality level is less than the first qualitylevel: set a next quality level equal to the second quality level, thenext quality level being representative of a next media content segmentadapted to be transferred; B) else if the second quality level is higherthan the first quality level: determine a current client score based onaverage peak-signal-to-noise-ratio and maximum peak-signal-to-noise-ratio representative of all transferred media contentsegments starting from initiation of the session up until a time indexcorresponding to the next media content segment; determine a futureclient score based on the second quality level; a) if the future clientscore is greater than or equal to the current client score: determinewhether or not the network link can support the second quality level,wherein the determining comprises a function of network architecture ofthe network link; i) if the network link can support the second qualitylevel: set the next quality level equal to the second quality level; C)else: set the next quality level equal to the first quality level. 39. Anetwork adapted to transfer media content, comprising: one or morecontent-storage devices that are configured to store the media content,the media content comprising a set of available media content versions,each available media content version being associated with a qualitylevel, wherein a plurality of media content segments is adapted to betransferred, each media content segment being associated with equal orvarying quality levels and varying time indices; and one or more clientdevices that are configured to transfer the media content from the oneor more content-storage devices over a network link, the one or moreclient devices being further configured to perform the method of any oneof EEEs 1-35.

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1. A method for controlling adjustment of quality level of media contentadapted to be transferred over a network link, comprising: creating, ata server, an indication of availability that lists content availablefrom one or more content sources, the indication of availabilitycomprising at least: a description of two or more first quality levelsegments of a particular media content item and a description of two ormore second quality level segments of the particular media content item,wherein at least one or more first quality level segments of the two ormore first quality level segments represent a same content portion ofthe particular media content item as at least one or more second qualitylevel segments of the two or more second quality level segments, whereinthe two or more first quality level segments of the particular mediacontent item require a first data rate, wherein the two or more secondquality level segments of the particular media content item require asecond data rate; causing the indication of availability to be sent to aclient device among a plurality of client devices; and wherein theclient device requests, from a content source of the one or more contentsources selected from the indication of availability, a first segmentfrom the two or more first quality segments of the particular mediacontent item or from the two or more second quality segments of theparticular media content item, based on available bandwidth over thenetwork link.
 2. The method of claim 1, wherein the server modifies theindication of availability to remove one or more descriptions thatcannot be used due to available data rate limitations of the networklink.
 3. The method of claim 1, wherein the server modifies theindication of availability to restrict descriptions made available to aspecific client device.
 4. The method of claim 1, wherein the servermodifies the indication of availability to restrict descriptions madeavailable to a specific client device to ensure bandwidth is availableacross the network link in the future.
 5. The method of claim 1, whereinthe indication of availability informs the plurality of client devicesthat available data rate of the network link has changed.
 6. The methodof claim 1, wherein the indication of availability includes an updateinterval element that informs the plurality of client devices when toupdate the indication of availability in a given interval.
 7. The methodof claim 1, wherein the client device periodically measures availablebandwidth over the network link.
 8. One or more non-transitorycomputer-readable storage media, storing one or more sequences ofinstructions, which when executed by one or more processors causeperformance of: creating, at a server, an indication of availabilitythat lists content available from one or more content sources, theindication of availability comprising at least: a description of two ormore first quality level segments of a particular media content item anda description of two or more second quality level segments of theparticular media content item, wherein at least one or more firstquality level segments of the two or more first quality level segmentsrepresent a same content portion of the particular media content item asat least one or more second quality level segments of the two or moresecond quality level segments, wherein the two or more first qualitylevel segments of the particular media content item require a first datarate, wherein the two or more second quality level segments of theparticular media content item require a second data rate; causing theindication of availability to be sent to a client device among aplurality of client devices; and wherein the client device requests,from a content source of the one or more content sources selected fromthe indication of availability, a first segment from the two or morefirst quality segments of the particular media content item or from thetwo or more second quality segments of the particular media contentitem, based on available bandwidth over the network link.
 9. The one ormore non-transitory computer-readable storage media of claim 8, whereinthe server modifies the indication of availability to remove one or moredescriptions that cannot be used due to available data rate limitationsof the network link.
 10. The one or more non-transitorycomputer-readable storage media of claim 8, wherein the server modifiesthe indication of availability to restrict descriptions made availableto a specific client device.
 11. The one or more non-transitorycomputer-readable storage media of claim 8, wherein the server modifiesthe indication of availability to restrict descriptions made availableto a specific client device to ensure bandwidth is available across thenetwork link in the future.
 12. The one or more non-transitorycomputer-readable storage media of claim 8, wherein the indication ofavailability informs the plurality of client devices that available datarate of the network link has changed.
 13. The one or more non-transitorycomputer-readable storage media of claim 8, wherein the indication ofavailability includes an update interval element that informs theplurality of client devices when to update the indication ofavailability in a given interval.
 14. The one or more non-transitorycomputer-readable storage media of claim 8, wherein the client deviceperiodically measures available bandwidth over the network link.